Immigrants from European nations began flocking to America's shores centuries ago to seek out better lives. These days, this list of countries is longer and the reasons more complex, but the substance of what American citizenship entails has remained largely unchanged. Many rights and responsibilities of being an American citizen are spelled out by the U.S. Constitution.
The main rights of American citizens are spelled out in the Constitution's original Bill of Rights. The freedoms of religion and speech ensure Americans the right to worship as they choose and to develop their own belief systems. Additionally, freedom is extended to the press, which has the right to question the government openly. Citizens are permitted to assemble for a cause so long as no violence ensues and are also allowed to voice these views to their elected officials. The Second Amendment gives the right to keep and bear arms--to have firearms and to use them, if necessary. The Fifth Amendment addressed legal issues, including the right to the due process of law and freedom from self-incrimination. The Sixth, Seventh and Eighth Amendments expanded upon the Fifth, adding the rights to a speedy trial and to a trial by jury and freedom from "cruel and unusual" punishment, among others. The right to privacy first came up in the Ninth Amendment, which applies to implications brought about by "unlisted" rights.
Perhaps the most contentious issue over the course of the United States' existence, the right to vote made its first appearance in the Constitution in the 15th Amendment, wherein it gave this right to every man, regardless of "race or color." Later amendments would make the right applicable to every citizen over the age of 18, although certain restrictions--namely, that convicted felons may not vote--do apply.
Responsibilities as listed in the Constitution are mainly implicit. They broadly expect that individuals should follow the letter of the law, fulfill their tax obligations, serve in the military (if deemed necessary, by an act of war for instance) and appear for jury duty when called. The explicit mention of the crime of treason--disloyalty--in the Constitution suggests that loyalty and patriotism must be a duty as well.
Steve Mount of The Constitution Online notes that the Constitution is "peppered with amendments that expanded the right to vote." He points out that "with few exceptions, all persons, 18 or older, can vote in any public election" and thereby concludes that voting, too, is a responsibility.
While, according to The Constitution Online, an explicit list of duties expected of citizens under the Constitution does not exist, Everyday Civics classifies the aforementioned responsibilities as "civic duties" and that "citizens who choose not to fulfill [them] face legal consequences."
Duties imply legal responsibilities in response to the rights guaranteed by the Constitution. Obligations imply moral responsibilities to the country and fellow citizens in response to having the privileges of citizenship. According to the business American Family Traditions, those obligations include being a volunteer and addressing the special needs of our communities; being a good neighbor and ensuring the safety and cleanliness of both our neighborhoods and our workplaces; and being a good American by living the principles and values consistent with those implied in the Constitution: integrity, self-discipline, proactivity, humility and empathy.